An optical fingerprint imaging system can implement fingerprint image capturing based on light reflection/refraction, and light sensoring. Specifically, when a finger touches an active area of the optical fingerprint imaging system, light emitted from the fingerprint imaging system will reach the finger and be reflected by the finger. As light reflected by different regions, e.g., ridges and valleys of the finger may have different intensity values, features of a fingerprint corresponding to the finger can be represented based on the light intensities. In some solutions, the reflected light may be received by a sensor where the intensity information thereof is converted into electrical signals. As such, a fingerprint image can be obtained based on processing the electrical signals.
Referring to FIG. 1, an existing optical fingerprint imaging system 100 is illustrated. The optical fingerprint imaging system 100 includes a light source 101, a light guide plate 102, and a sensor 103. The light source 101 is disposed on a lateral side of the light guide plate 102, and the light guide plate 102 is disposed below a first surface of the sensor 103. Accordingly, light emitted from the light source 101 enters into the light guide plate 102, and then is guided by the light guide plate 102 to upwardly penetrate the sensor 103. Thereafter, the light comes out from a second surface of the sensor unit 103. The second surface of the sensor 103 is located opposite to the first surface of the sensor 103, which is facing the exterior of the system.
Furthermore, the light guide plate 102, which is employed for guiding the light emitted from the light source 101 to an active surface (e.g. the second surface), generally has a thickness greater than 0.4 mm, which occupies a considerable portion of the entire thickness of the optical fingerprint imaging system.
Therefore, an optical fingerprint imaging system, which has a reduced thickness and a simplified structure, is required.